Method of making cellular crosslinked poly(dicyclopentadiene)

ABSTRACT

Disclosed is an improved method of making a cellular crosslinked polymer with a metathesis-catalyst system where a metathesis-catalyst is activated with an alkylaluminum iodide compound. 
     In a preferred embodiment, two parts of the metathesis-catalyst system form the basis for two solutions, a catalyst/monomer solution and an alkylaluminum iodide activator/monomer solution. At least one solution also contains a blowing agent. The solutions are combined in one place, such as the mixing head of a reaction injection molding machine, and then injected into another place, such as a mold, where the monomer reacts to form a cellular crosslinked polymer.

This application is a continuation of application Ser. No. 552,872,filed Nov. 17, 1983, U.S. Pat. No. 4,458,037, issued July 3, 1984.

BACKGROUND OF THE INVENTION

This invention relates to the chemical arts. In particular, thisinvention relates to an improved method of making a cellular crosslinkedpolymer of dicyclopentadiene with a metathesis-catalyst system.

U.S. Pat. No. 4,002,815 discloses the use of a metathesis-catalystsystem which employs a dialkylaluminum iodide, an alkylaluminum diiodideor a mixture of trialkylaluminum compounds with elemental iodine toproduce substantially gel-free copolymers of cyclopentene anddicyclopentadiene.

U.S. application Ser. No. 526,835 filed Aug. 26, 1983 and assigned tothe same assignee, discloses a cellular crosslinkedpoly(dicyclopentadiene) which is made with a metathesis-catalyst system.The cellular polymer is made by injecting the catalyst system, whichincludes an alkylaluminum activator, into a reaction vessel which ispreheated, preferably to a temperature from about 100° C. to about 125°C.

Now it has been found that the activation of a metathesis-catalyst withan alkylaluminum iodide compound results in a catalyst system capable ofpolymerizing dicyclopentadiene monomer into a cellular crosslinkedpolymer having good uniformity of structure without having to preheatthe reaction vessel to high temperatures.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

In an improved method of making a cellular crosslinkedpoly(dicyclopentadiene), dicyclopentadiene monomer is catalyzed with atwo part metathesis-catalyst system, the first part ofmetathesis-catalyst, the second part an alkylaluminum iodide activator.In a preferred embodiment, the two metathesis-catalyst parts, plus themonomer and a blowing agent, form the basis of at least two separatereactant streams which can be mixed in one place, such as the mixinghead of a reaction injection molding machine, and then injected intoanother place, such as a mold, where the monomer sets up into a cellularcrosslinked polymer.

DETAILED DESCRIPTION OF THE INVENTION

A metathesis-catalyst system is employed to polymerize dicyclopentadienemonomer in such a manner that the resulting product is a cellularcrosslinked polymer. The preferred monomer is dicyclopentadiene(3a,4,7,7a-tetrahydro-4,7-methano-1H-indene).

In the preferred embodiment the cellular crosslinked polymer is formedentirely from dicyclopentadiene (hereinafter referred to as DCPD)monomer. In other embodiments the cellular crosslinked polyer is formedfrom DCPD monomer and up to about 20% of one or more other cycloolefinmonomers, where the cycloolefin monomer contains from about five toabout twelve carbon atoms. Representative cycloolefin monomers includenorbornene, norbornadiene, cyclopentene, dimethanehexahydronaphthalene,and dimethaneoctahydronaphthalene.

The polymerization of the DCPD is catalyzed by a two partmetathesis-catalyst system. One part contains a metathesis-catalyst suchas a tungsten containing metathesis-catalyst. The catalyst is preferablya tungsten halide or tungsten oxyhalide, most preferably WCl₆ or WOCl₄.

The other part contains an alkylaluminum iodide activator. Thealkylaluminum iodide activator is an alkylaluminum dihalide,dialkylaluminum halide or a mixture of a trialkylaluminum and elementaliodine, where the alkyl group contains one to twelve carbon atoms. Inthe preferred activators, the alkyl group is ethyl. The most preferredactivator is diethyl aluminum iodide.

The metathesis-catalyst, as described above, is preferably in solutionwith the monomer or mixture of monomer to be polymerized. In a preferredembodiment, a tungsten containing catalyst is first added to a smallamount of a solvent to form a slurry. The solvent must not besusceptible to reacting with the tungsten containing catalyst.Representative solvents include benzene, xylene, toluene, chlorobenzene,dichlorobenzene, trichlorobenzene and hexane. Sufficient solvent isadded so that the tungsten concentration is between about 0.1 and 0.7mole per liter of solvent.

The tungsten containing catalyst is then made soluble in the slurry bythe addition to the slurry of a small amount of an alcohol or a phenolcompound. Phenols are preferred. Suitable phenols include phenol,alkyl-phenols, and halogen containing phenols, with tert-butyl phenol,tert-octyl phenol and nonyl phenol being most preferred. The preferredmolar ratio of tungsten:phenol is from about 1:1 to about 1:3. Thecatalyst/phenol solution can be made by adding the phenol to thecatalyst slurry, stirring the resulting solution and then blowing astream of a dry inert gas through the solution to remove any gases whichmay be formed. Alternatively, a phenolic salt, such as a lithium orsodium phenoxide, can be added to the catalyst slurry, the mixturestirred until essentially all the catalyst is dissolved, and theprecipitated inorganic salt removed by filtration or centrifugation. Allof these steps should be carried out in the absence of moisture and airto prevent deactivation of the catalyst.

In some embodiments of the invention, it is desirable to increase theshelf-life of the catalyst solution. This is done by adding from about 1to about 5 moles of a complexing agent, such as a Lewis base or achelating agent, per mole of tungsten, to the tungsten containingcatalyst solution. Preferred Lewis bases include nitriles and etherssuch as benzonitrile and tetrahydrofuran. Preferred chelants includeacetylacetones and alkyl acetoacetates, where the alkyl group containsfrom one to ten carbon atoms.

The improvement in the shelf-life of the tungsten containing catalyst isobtained whether the complexing agent is added before or after thephenol is added.

The alkylaluminum iodide activator, as described above, is alsopreferably in solution with the monomer or mixture of monomers to bepolymerized. A rate moderator is often added to the activator/monomersolution so that when the activator is mixed with the catalyst/monomersolution, the polymerization does not initiate instantaneously and thepolymer is not formed too rapidly. The onset of polymerization isdelayed by adding a moderator to the activator/monomer solution. Ethers,esters, ketones and nitriles are representative rate moderators for thealkylaluminum compounds. Isopropyl ether, tetrahydrofuran andbenzonitrile are examples of preferred rate moderators. Ethyl benzoateand butyl ether are most preferred. The preferred ratio of thealkylaluminum iodide to rate moderator is from about 1:0.5 to about 1:5on a molar basis.

A blowing agent is incorporated into the catalyst system in order that aproduct having a cellular structure is formed during polymerization. Anyof the conventional blowing agents used in reaction injection molding(hereinafter referred to as RIM) processes or related processes may beemployed provided that the blowing agent does not poison or otherwiseadversely affect the metathesis-catalyst system. Preferred blowingagents include low boiling organic compounds, i.e. compounds which areliquids under ambient conditions but which are volatilized underpolymerization conditions, and inert gases. Representative low boilingorganic compounds include hydrocarbons such as pentane and hexane, andhalogenated hydrocarbons such as methylene chloride andtrichlorofluoromethane. Representative inert gases include nitrogen,argon and fluorinated hydrocarbons, such as dichlorodifluoromethane.

The blowing agent is incorporated into either or both parts of themetathesis-catalyst system, or it may be added to the monomerseparately. The amount of blowing agent to be incorporated is from about2 to about 30, preferably from about 5 to about 20, percent by weightbased on the weight of the monomer. The greater the amount of blowingagent used the less dense the final cellular crosslinked polymerproduced.

The components of the catalyst system of this invention are combined sothat the resulting DCPD to tungsten ratio, on a molar basis, is fromabout 1,000:1 to about 10,000:1, preferably about 2,000:1 and so thatthe resulting aluminum to a tungsten ratio, on a molar basis, will befrom about 2:1 to about 20:1, preferably about 10:1.

The exact amounts of catalyst, alkylaluminum iodide, activator andblowing agent to be incorporated into a given catalyst system willdepend on the particular catalyst, alkylaluminum iodide activator andblowing agent chosen as well as the desired final product. The amountswill be readily determinable by one skilled in the art without undueexperimentation following the teachings of this specification.

In some embodiments, the cellular crosslinked polymer of this inventionis made and molded by RIM or related processes. The two parts of themetathesis-catalyst system are separately mixed with monomer and blowingagent to form two stable solutions which are placed in separate vessels.These vessels provide the source for separate streams. The two streamsare combined in one place, such as a RIM machine's mixing head, and theninjected into a second place, such as a mold where polymerization takesplace.

The invention is not intended to be limited to embodiments employing twostreams each containing monomer and blowing agent. It will be obvious toone skilled in the art that there may be situations where it isdesirable to have monomer incorporated in just one stream or to employ aplurality of streams where the additional streams contain monomer oradditives or both.

In a preferred embodiment, the streams are combined in the mixing headof a RIM machine. Mixing is easy to achieve because the process involveslow molecular weight, rapidly diffusing components. Typically the mixingheads have orifices about 0.032 inch in diameter are a jet velocity ofabout 400 ft/sec. After being combined, the mixture is injected into amold maintained from about 30° C. to about 80° C. The mold pressure isin the range of about 10-15 psi. A rapid exothermic reaction occurs.Typically, the cellular crosslinked polymer is formed in from about 10seconds to about 10 minutes. It has been found that exotherm caused bythe polymerization is sufficiently great and occurs at the proper timeso that it is not necessary to preheat the mold to temperatures greaterthan about 80° C.

In some embodiments a nucleating agent, such as calcium carbonate, isadded to at least one of the reactant streams. The nucleating agentaffects the structure of the foam by helping to make the foam cellssmall and uniform. Other suitable nucleating agents include talc,magnesium carbonate, barium carbonate, zinc carbonate, lead carbonate,magnesium oxide, calcium oxide, barium oxide, zinc oxide, lead oxide andsilica. The preferred nucleating agent is silica.

In some embodiments, a preformed elastomer is added to themetathesis-catalyst system. The addition of an elastomer serves toincrease the viscosity of the reactant streams and improve the impactresistance of the final polymeric product. The elastomer can bedissolved in either or both of the reactant streams in an amount of fromabout 3 to about 15 weight percent based on weight of the monomer.Illustrative elastomers include natural rubber, butyl rubber,polyisoprene, polybutadiene, polyisobutylene, ethylene-propylenecopolymer, styrene-butadiene-styrene triblock rubber, randomstyrene-butadiene rubber, styrene-isoprene-styrene triblock rubber andethylene-propylene diene terpolymers. The amount of elastomer used isdetermined by its molecular weight and is limited by the viscosity ofthe resultant reactant streams. The reactant streams containingelastomer cannot be so viscous that mixing is not possible. Although theelastomer can be dissolved in either one or both of the streams, it isdesirable that it be dissolved in both.

In some embodiments the reactant streams and consequently the finalpolymer may also contain fillers. Representative fillers include glass,wollastonite, mica, carbon black, talc and calcium carbonate.

The best mode now contemplated of carrying out this invention isexemplified by the following working examples of preferred specificembodiments. This invention is not limited to these specific examples.All weights and volumes are percentages, based on the weight or volumeof DCPD unless otherwise clearly indicated.

EXAMPLES 1-3

Examples 1-3 illustrate preferred embodiments of polymerizing DCPD to acellular crosslinked polymer using a tungsten hexachloride catalyst, adiethylaluminum iodide activator, a blowing agent, a nucleating agentand optionally a styrene-butadiene random rubber.

In each example, 1-3, 0.5 g. of a fine particulate silica is added to a25×150 mm test tube which is then capped and inerted with nitrogen. 10g. of DCPD is then syringed into the capped test tube. In examples 2 and3, styrene-butadiene random rubber is dissolved in the DCPD prior to theaddition of DCPD to the test tube. Next, a blowing agent is added to thetest tube by transferring a measured volume of condensed liquid througha stainless steel cannula. The contents are then heated to 40° C. byplacing the test tube in a heated bath. 0.13 ml of a 0.85 molar solutionof diethylaluminum iodide in toluene which also contains butyl ether, ina diethylaluminum iodide to butyl ether molar ratio of 1:1.2, is thenadded to the heated mixture. Finally, 0.38 ml of a 0.1 molar solution oftungsten hexachloride/nonylphenol/acetylacetone, having a molar ratio of1:1:2, in toluene is added to the heated mixture. The contents are thenmixed with a vortex mixer. The test tube is vented and the contentsallowed to polymerize and expand into a cellular crosslinkedpoly(dicyclopentadiene). Table 1 indicates the particular blowing agentand amount used as well as the amount, if any, of styrene-butadienerandom rubber dissolved in the dicyclopentadiene.

                  TABLE 1                                                         ______________________________________                                        Examples        1         2        3                                          ______________________________________                                        DCPD, grams     10.0      10.0     10.0                                       0.1 M WCl.sub.6 solution (ml)                                                                 0.38      0.38     0.38                                       0.85 M Et.sub.2 AlI solution (ml)                                                             0.13      0.13     0.13                                       Silica (weight percent)                                                                       0.5.sup.(1)                                                                             0.5.sup.(2)                                                                            0.5.sup.(3)                                Blowing agent   CFCl.sub.3                                                                              CH.sub.2 Cl.sub.2                                                                      CF.sub.2 Cl.sub.2                          (volume percent)                                                                              15        5        5                                          Styrene-butadiene random                                                                      --        3        6                                          rubber (weight percent)                                                       ______________________________________                                         .sup.(1) Cabosil MS5 (manufactured by Cabot Corp., Boston, MA)                .sup.(2) Cabosil EH5 (manufactured by Cabot Corp., Boston, MA)                .sup.(3) Cabosil MS7 (manufactured by Cabot Corp., Boston, MA)           

EXAMPLE 4

This example illustrates a preferred embodiment of the synthesis ofcellular poly(DCPD) via reaction injection molding where the catalystsystem is activated with diethylaluminum iodide (Et₂ AlI).

Poly(DCPD) is made using a standard RIM machine manufactured byAccuratio Co. of Jeffersonville, Ind. Into two tanks having a capacityof two gallons each is charged DCPD containing 6% by weight of a randomstyrene-butadiene rubber. The tanks are then closed and inerted withnitrogen. Sufficient Et₂ AlI is transferred into one of the tanks tobring the Et₂ AlI concentration to 0.053 molar and sufficient di-n-butylether added to the same tank to achieve an ether to Et₂ AlI ratio of1.2:1. Next, to the other tank is added sufficient WCl₆/nonyl-phenol/acetylacetone catalyst, having a molar ratio of 1:1:2, intoluene to provide a 0.0071 molar concentration. Added to each tank issufficient fluorotrichloromethane to achieve a concentration of 5 partsper hundred, based on the weight of the DCPD, and sufficient fineparticulate silica (Cab-O-Sil EH-5, manufactured by Cabot Corp., Boston,Mass.) to achieve a concentration of 0.5 parts per hundred, based on theweight of DCPD. All transfers are done in a way to preclude the entranceof oxygen or moisture into the system. The materials are then thoroughlyblended in their respective tanks.

The components of the two tanks are combined in a standard impingementtype RIM mixhead. The ratio of the activator/monomer solution mixed withcatalyst/monomer solution is 1:1. The impingement mixing is accomplishedby passing both the solutions through orifices 0.032" in diameter at aflow rate approximately 80 ml/sec. This requires pumping pressure ofapproximately 1000 psi.

The resulting mixture flows directly into a mold heated between 40° C.and 80° C. The mold is made out of chrome plated aluminum. The mode hasa flat cavity which forms a plaque sample 10"×10"×1/8" thick. A clampingforce of 1.5 tons is used to keep the mold closed. The reactantspolymerize rapidly in the closed mold, reaction being substantiallycomplete in about two minutes. The mold is open and a cellular DCPD isrecovered. A cellular crosslinked DCPD is formed.

What I claim and desire to protect by Letters Patent is:
 1. A foamedcross-linked polymerized dicyclopentadiene polymer compositioncomprising:(a) cross-linked polymerized dicyclopentadiene polymer; and(b) a dialkylaluminum iodide component.
 2. The composition of claim 1further comprising an elastomer.
 3. The composition of claim 1 furthercomprising at least one additional polymerized cycloolefin.
 4. Thecomposition of claim 1 wherein said dialkylaluminum iodide compound isdiethylaluminum iodide.
 5. The composition of claim 3 wherein saidcycloolefin is norbornene, norbornadiene or cyclopentadiene.
 6. Apolymerization feed composition comprising dicyclopentadiene and adialkylaluminum iodide compound.
 7. The composition of claim 6 whereinsaid dialkylaluminum iodide compound is diethylaluminum iodide.
 8. Thecomposition of claim 6 further comprising an elastomer.
 9. Thecomposition of claim 6 further comprising a catalyst.
 10. Thecomposition of claim 6 further comprising at least one additionalcycloolefin monomer.
 11. The composition of claim 9 wherein saidcatalyst is WCl₆ or WOCl₄.
 12. The composition of claim 10 wherein saidadditional cycloolefin monomer is norbornene, norbornadiene orcyclopentene.